TENS on salivary flow and voice

ABSTRACT Electrical stimulation has shown potential in improving salivary flow in patients with head and neck cancer, but its impact on post-radiotherapy voice is not yet fully understood. This is a case series involving three men and one woman with an average age of 58 years and 2.5 months, who underwent chemotherapy and radiotherapy for oropharyngeal tumors, presenting with vocal complaints and hyposalivation. All subjects underwent nasofibrolaryngoscopy, voice recording, and salivary flow measurement at the beginning and end of treatment. Perceptual-auditory and acoustic voice analyses were performed. The aim was to compare the results of salivary volume and vocal measures before and after electrical stimulation. After the intervention, there was a variable increase in salivary flow in all patients, with an average of 0.66 ml/min; however, no marked differences were observed in the perceptual-auditory voice evaluation, as they were very subtle. Nevertheless, changes were recorded in the acoustic analysis of glottal source (changes in fundamental frequency, with a more evident increase, and reduction in some parameters) and in the spectrographic analysis using Wide Band Spectrography. Improvement was observed, with a reduction in antiresonance at low and high frequencies. In Narrow Band Spectrography, there was a worsening, with a reduction in the definition and regularity of harmonics at low and mid frequencies and across the entire spectrogram, as well as a reduction in the number of harmonics at mid frequencies and across the entire spectrogram. Improvement was recorded with a reduction in noise (general) and sub-harmonics at high frequencies. Electrical stimulation demonstrated the ability to induce a variable increase in salivary flow with some acoustic vocal improvements, while the perceptual-auditory voice evaluation did not reveal differences between pre- and post-intervention moments. Despite the promising results, studies with larger samples and greater control of intervening variables are crucial to establish a causal relationship between saliva induced by electrical stimulation and the improvement of vocal quality in patients undergoing radiotherapy.